Pneumatic motor governor

ABSTRACT

A pneumatic motor governor including a valve port located in the motor supply passage and axially aligned with the motor. The end of the motor carries a spindle and a closed end valve sleeve is slidably mounted on the spindle to reciprocate toward and away from the valve port to throttle air flowing through the port and between the port and the closed end of the valve sleeve. The closed end of the sleeve includes a small hole to allow the air pressure beneath the closed end to balance itself with the pressure on the top or outer face of the closed end, thereby preventing the air pressure in the inlet air from creating forces interfering with the free operation of the valve sleeve. The valve sleeve is moved back and forth by a system of conventional flyweights mounted on the motor spindle.

United States Patent Tibbott [451 Oct. 10, 1972 PNEUMATIC MOTOR GOVERNOR Primary Examiner-C. J. Husar 72 Inventor: David w. Tibbott, Phillipsburg, NJ. "Often, David Tibbn and 7 Frank S. Troidl [73] Assignee: Ingersoll-Rand Company, New

I [57] ABSTRACT Filed} March 1971 .A pneumatic motor governor including a valve port located in the motor supply passage and axially 21 A l. N l 1 pp 0 127393 aligned with the motor. The end of the motor carries a spindle and a closed end valve sleeve is slidably [52] U.S.Cl. AIS/36, 137/53, 173/12, mounted on the spindle to reciprocate toward and I 415/25 away from the valve port to throttle air flowing [51] Int. Cl ..F01b 25/06 through the port and between the port and the closed [58] Field of Search ..415/25, 36; 173/12; 137/53 end of the valve sleeve. The closed end of the sleeve includes a small hole to allow the air pressure beneath 5 References Cited the closed end to balance itself with the pressure on the top or outer face of the closed end, thereby UNITED STATES PATENTS preventing the air pressure in the inlet air from creating forces interfering with the free operation of the 553:? et valve sleeve. The valve sleeve is moved back and forth by a system of conventional flyweights mounted on the motor spindle.

7 Claims, Drawing V Q u l0 A? fl A as, I34 l I4" 23 25 i 2 29 22 2 28 27 20 l6 1%; r 20 2 g I? I5 r I l r 3 '8 PNEUMATIC MOTOR GOVERNOR BACKGROUND OF INVENTION This invention relates to pneumatically operated motors such as used in power tool and more particularly to a governor valve for controlling the speed of a pneumatic motor.

1 A conventional governor for a pneumatic motor includes a valve sliding in a sleeve and controlling a side port in the sleeve to meter air to the motor in response to its speed. This type of governor valve is known as a sleeve-type governor. The operation of a sleevetype governor depends on the ease that the valve can slide in the sleeve and dirt is likely to build up on the sliding surfaces between the sleeve and valve to interfere with the proper operation of the valve.

Another type of governor valve is known as a facetype" governor. An example of this type of governor is shown in US. Pat. No. 2,925,089 issued Feb. 16, 1960 to RM. Conklin et al. This type of valve uses a sliding sleeve approaching an axially aligned port and throttling the air flowing between the end of the sleeve and the port. The sleeve is open-ended and slides on a rotating spindle fixed on the end of an air motor. Since the sleeve is open-ended, dirt in the air stream can be easily deposited on the sliding surfaces between the sleeve and the spindle to interfere with the properoperation of the valve, although itis believed that the face-type governor is less susceptable to dirt than the sleevetype governor.

SUMMARY OF INVENTION The principal object of this invention is to provide an improved face-type governor which is less susceptable to dirt than either the sleeve-type governor or previous face-type" governors while performing as well as previous face-type governors.

In general, the improved governor valve of this invention modifies the open-ended sleeve of the earlier type of face-type governor by covering its throttling end and adding a small hole in the cover to allow the air pressure to be balanced on both faces of the sleeve cover. The small air balancing hole allows only a slight amount of dirt in the air stream to penetrate to the sliding surfaces of the governor. In addition, the air balancing hole can be covered to prevent the direct impingement of dirt in the air stream on the open hole, thus further reducing the amount of dirt entering the port while allowing the hole to freely perform its air balancing function.

BRIEF DESCRIPTION OF DRAWING The invention is described in connection with the accompanying drawing wherein:

FIG. 1 is a fragmentary andaxial section of the rear portion of an air-operated grinder incorporating the governor valve of this invention;

' FIG. 2 is a cross-section taken on the line 22 in FIG. 1; and

FIGS. 3 to 5 are fragmentary axial sections of additional embodiments of the governor valve.

DESCRIPTION OF PREFERRED EMBODIMENTS The first embodiment of the invention is shown in FIGS. 1 and 2 installed in a portable pneumatic tool 1,

such as a grinder, including a casing 2 containing a motor 3, a motor rotor 4, a fluid supply passage 5 extending from a hose connection 6 at the rear end of the tool 1 to the motor 3 and a throttle valve 7 operated by a throttle lever 8 and located in the supply passage 5 to control the fluid flowing through the supply passage 5. All of the foregoing elements are conventional in prior art grinders of a similar type.

The supply passage includes a valve bushing 10 threaded into the casing 2 in axial alignment with the rear end of the motor rotor 4 to serve as a valve port 11, provided by the bore in the bushing 10. The motor end 12 of the bushing 10 is beveled around its outer edge to provide a relatively thin edge on the end 12. The bushing 10 can be threaded back and forth in the casing 2 for adjustment purposes. The port 11 opens into an enlarged governor chamber 14 located immediately to the rear of the motor 3 and communicating with the inlet 15 of the motor 3.

A spindle 16 is threaded into the 'rear end of the motor rotor 4 and extends rearwardly into the chamber 14 where it is axially aligned with the valve port 1 1. The spindle 16 rotates with the motor rotor 4 and includes a flange 17 extending radially outward from it and surrounding it immediately to the rear of the bearing 18 for the motor rotor 4. Four flyweight levers 20 are pivoted on the flange 17 at equally spaced positions around the spindle 16. Each flyweight lever 20 includes a lever arm 21 extending radially inward to operate a governor sleeve 22 sliding on the spindle 16. The forward end of the governor sleeve 22 engages the lever arms 21 and is pushed rearwardly by the flyweights 20 as they pivot outward in response to an increased speed of the motor rotor 4.

The governor sleeve 22 is resiliently urged forward by a mechanism housed in the spindle 16. A bolt 26 slides in the hollow spindle l6 and carries a head 27 at its rear end that is connected to the sides of the governor sleeve 22 by a diarnetically extending pin 28. The pin 28 slides in longitudinally extending slots 29 provided in the sides of the spindle 16 whereby the valve 22 and pin 28 are free to move back and forth on the spindle 16 for a limited distance. The forward end of the bolt 26 carries a spring 30 captured between its nut 31 and the forward end of the spindle 16. The compression load on the spring is controlled by the position of the nut 31 on the bolt.

The inner diameter of the governor sleeve 22 is substantially equal to the inner diameter of the valve port 1 l. The sleeve 22 is closed at its rear end by a cover 23 with the cover 23 cooperating with the rear end of the spindle 16 to enclose a space 25 beneath the cover 23. The fit between the interior of the sleeve 22 and the spindle 16 should be fairly close to avoid substantial leakage between these faces from the space 25.

The novel invention in this application is the idea of providing the sleeve cover 23 with a small axial hole 33 for allowing the pneumatic pressure on both faces of the cover 23 to be automatically balanced during operation of the governor. To aid in preventing dirt from freely entering the hole 22, it is surrounding by a raised lip 34 projecting rearwardly to deflect dirt impinging on the cover 23.

The operation of the foregoing governor mechanism is believed to be obvious. Normally, the spring 30 urges the governor sleeve 22 forwardly toward the position shown in FIG. 1, to maintain the valve port 11 open. As the speed of the motor 3 increases, centrifugal force on the flyweight 20 causes them to attempt to tilt radially outward with the flyweight arms 21 moving rearwardly and urging the governor sleeve 22 rearwardly against the force of the spring 30. As the governor sleeve 22 moves rearward, it restricts the air flowing from the port 11. Ultimately, the valve sleeve 22 reaches a location where the speed of the motor 3 balances the amount of supply air flowing by the governor. This type of operation is conventional in the art of pneumatic governors.

It has been determined that the foregoing construction of a face-type governor operates as well as previous types of face-type governors while being less likely to be disabled by dirt. It is easily seen that the only dirt that is likely to enter the hole 33 is dirt moving in the air stream flowing through the valve port 11 and that happens to be located in the air stream where it will impinge directly on the small area bounded by the sides of the hole 33. As compared to the prior art wherein the entire end of the governor sleeve is open, this invention greatly minimizes the amount of dirt that can reach the sliding surfaces of the governor sleeve 22.

The embodiment shown in FIG. 3 adds a cap 35 that is spaced from and overhangs the pressure balancing hole 33. The cap is attached to the cover 23 at one side of the hole 33 and shields the hole 33 from dirt impinging directly on the hole.

Another embodiment is shown in FIG. 4 wherein a hollow tube 37 is attached to the cover 23 around the hole 33 and projects rearwardly into the valve port 11. The tube 37 is closed at its rear end and carries a radial passage 38 adjacent its end whereby pressure around the tube 37 is in communication with the space 25 beneath the cover 23. The purpose of this embodiment is the same as the FIG. 3 embodiment, namely, to shield the hole 33 from dirt in the air stream. Dirt is not likely to enter the passage 38 in the tube 37. In addition, applicant believes that any dirt entering the passage 38 will be engaged by the rotating walls of the passage 38 (the tube 37 rotates with the governor sleeve 23) and will be thrown from the passage 38 by centrifugal force.

The embodiment shown in FIG. includes a detachable cover 40 on the rear end of the governor sleeve 22 in place of the integral cover 23. The detachable cover 40 fits over the end of the sleeve 23 and is held in place by a tight frictional engagement. This embodiment may be useful in certain designs of the governor sleeve 22 for easily assembling the governor.

It is important that the space 25 beneath the cover 23 be substantially closed to leakage, except for the hole 33 so that the pressure on both faces of the cover can become balanced.

Although several embodiments of the invention are illustrated and described in detail, it will be understood that the invention is not limited simply to these embodiments but contemplates other embodiments and variations which utilize the concepts and teachings of this invention.

I claim: 1 I 1. In combination with a pressure fluid driven motor including a casing, a fluid driven motor mounted for rotation in said casing and a supply passage in said casing for feeding pressure fluid to said motor, the invention comprising:

a spindle on said motor rotor mounted to rotate with the rotor;

a valve port located in and forming a portion of said supply passage whereby fluid in said passage flows through said port in flowing to said motor, said port being axially aligned with said spindle;

a valve sleeve sliding on said spindle adjacent said port whereby it can slide toward said port to throttle fluid flowing from the end of said port, the throttled fluid flowing radially outward from the end of said port between said port and the adjacent end of said sleeve;

flyweight means on said spindle for moving said sleeve towards said port in response to the rotary speed of said motor rotor;

means for resiliently urging said sleeve away from said port; and

a cover fixed on the end of said sleeve between the spindle and the port and containing a small hole to balance the fluid pressure on both faces of said cover.

2. The combination of claim 1 wherein: said cover is detachably mounted on said sleeve.

3. The combination of claim 1 wherein: said cover is an integral end on said sleeve.

4. The combination of claim 1 including: protection means on said cover to prevent dirt in the fluid flowing through said valve port from impinging directly on said hole in said cover.

5. The combination of claim 4 wherein:

said protection means includes a cap overhanging the end of said hole and mounted on said cover wherein said cap shields the hole from dirt in said fluid flowing through said port.

6. The combination of claim 4 wherein:

said protection means includes a hollow tube mounted on said cover over said hole to communicate with said hole and extending into said valve port.

7. The combination of claim 6 wherein:

said tube is closed at its free end positioned in said valve port and includes an opening adjacent its free end communicating with its hollow interior. 

1. In combination with a pressure fluid driven motor including a casing, a fluid driven motor mounted for rotation in said casing and a supply passage in said casing for feeding pressure fluid to said motor, the invention comprising: a spindle on said motor rotor mounted to rotate with the rotor; a valve port located in and forming a portion of said supply passage whereby fluid in said passage flows through said port in flowing to said motor, said port being axially aligned with said spindle; a valve sleeve sliding on said spindle adjacent said port whereby it can slide toward said port to throttle fluid flowing from the end of said port, the throttled fluid flowing radially outward from the end of said port between said port and the adjacent end of said sleeve; flyweight means on said spindle for moving said sleeve towards said port in response to the rotary speed of said motor rotor; means for resiliently urging said sleeve away from said port; and a cover fixed on the end of said sleeve between the spindlE and the port and containing a small hole to balance the fluid pressure on both faces of said cover.
 2. The combination of claim 1 wherein: said cover is detachably mounted on said sleeve.
 3. The combination of claim 1 wherein: said cover is an integral end on said sleeve.
 4. The combination of claim 1 including: protection means on said cover to prevent dirt in the fluid flowing through said valve port from impinging directly on said hole in said cover.
 5. The combination of claim 4 wherein: said protection means includes a cap overhanging the end of said hole and mounted on said cover wherein said cap shields the hole from dirt in said fluid flowing through said port.
 6. The combination of claim 4 wherein: said protection means includes a hollow tube mounted on said cover over said hole to communicate with said hole and extending into said valve port.
 7. The combination of claim 6 wherein: said tube is closed at its free end positioned in said valve port and includes an opening adjacent its free end communicating with its hollow interior. 